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Determination of Maximum Shear Modulus and Constraint Modulus in Unsaturated Sandy Soil under Hydraulic Hysteresis in Different Degree of Saturations

Jahed Orang, Milad | 2017

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 49710 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Jafarzadeh, Fardin
  7. Abstract:
  8. One of the most important parameters in dynamic analysis is small-strain shear modulus of soils (Gmax). Additionally, due to the seasonal variations and traffic loading, determination of constraint modulus (M) of subragde soils is of great importance. Seasonal Variations such as evaporation, evapotranspiration and precipitation causes subgrade soils to be on unsaturated state. Therefore, there is an extending need to study the influence of matric suction and degree of saturation on maximum shear modulus and constraint modulus in the design and analysis of earthen structures.In this study, we employed a dynamic simple shear apparatus in order to fully understand variations of Gmax and M with respect to different matric suctions. Measurements of shear and pressure wave velocities are obtained by the use of bender and extender elements. These elements are contained in top and bottom cap of the dynamic simple shear apparatus. Having both these velocities, we can measure maximum shear and constraint modulus. Two sets of tests are conducted with different relative densities (i.e. 30% and 75%). Both tests are in K0 consolidation state and net consolidation stress is equal to 50 kPa. These tests peroformed on Babolsar sand to analyze the impact of drying- wetting- scanning paths (hydraulic hysteresis) on small-strain shear modulus and constraint modulus. These paramaters were measured by continuous changes in degree of saturation under controlled matric suctions.Results have shown that hydraulic hysteresis can have a significant impact on the values of Gmax and M. Measured values with continuous changes in degree of saturation are in good agreement with variational trends of these parameters with respect to matric suction. Moreover, it is concluded that drying- wetting paths lead to a greater value of maximum shear and constraint modulus in scanning path. It is also important to notice that Gmax and M values obtained for higher relative density (i.e. 75%) are higher than corresponding values in low relative density (i.e. 30%)
  9. Keywords:
  10. Dynamic Simple Shear Apparatus ; Babolsar Sand ; Maximum Shear Modulus ; Bender Element Test ; Hydraulic Hystersis ; Extender Element ; Maximum Constraint Modulus

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